Twin-propeller aeroplane



L. B. SPERRY.

TWIN PROPELLER AEROPLANE.

APPLICATION FILED 0CT.19| 1917.

Patented Sept. 21, 1920.

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LAWRENCE B. SPERRY, OF BROOKLYN, NEW YORK, ASSIGNOR TO THE LAWRENCE SPERRY AIRCRAFT COMPANY, INC., OF NEW YORK, N. Y.,

YORK.

TWIN-PROPELLER AEBOPLANE.

Patented sept. 21., i920.

Application `ileri October 19, 1917. Serial No. 197,388.

To all whom t may concern Be it known that I, LAWRENCE B. SPERnY, a citizen of the United States of America, residing at 1505 Albemarle road, Brookl n, in the county of Kings and State of ew York, haveinvented certain new and useful Improvements in Twin-Propeller Aeroplanes, of which the following is a specifica-- tion. D

This invention relates to the stabilization of aeroplanes, not against sudden and natural atmospheric disturbances, but against the increase of depressing currents of air produced by the planes when the propeller or propellers are in rotation. These currents acting upon the elevating rudders of the craft exert an appreciable downward pressure on said rudders and on the tail of the machine, especially in the tractor type of biplanes, since the propeller accelerates the passage of air through the planes.

The object of the invention is to neutralize the downward pressure of the air in the immediate vicinity of the said rudders. The preferred manner in which this'is done 1s fully pointed outv in the following speclfication.-

Referring to the drawings, Figure 1 1 s a side elevation of an aeroplane embo'dyin my invention; Fig. 2 is alrear elevation of f the same showing the position of the propel- 1ers and the method of mounting them. Fig. 3 is a top plan view of the same aeroplane. Fig. 4 is a diagrammatic View showing a modiication in the relative position of the propellers and the elevating rudders. Fig. 5 is a detail showing a method of adjusting the horizontal tail plane.. Fig. 6 shows a modified position of the tail planes.

My invention in its preferred form, is embodied in a multiple propeller tractor type of biplane. The driving motors 1 and 2 are shown mounted on leither side of the body or fuselage 3 of the craft which is provided withupper-and lower supporting wings 8` and 18. Said motors are provided with propellers 4 and-:5. The propellers are oppositely pitched, and are designed to be revolved by the engines `in opposite directions,

aeroplane, or be provided with large enough propellers, to cause the blades of the propeltionof planes l1 may,

1ers to sweep close to the body of the` aeroplane and comparatively closely together. The a1r str1king the under side 7 of the upper wing 8 of the aeroplane, is deflected, so that as it leaves the rearpart 9 of the wing, it takes a downward trend'as indicated by the arrows 10, Fig. 1. This stream of air bears down on the horizontal tail surfaces 11, thus acting as a heav weight on v the rear end of the aeroplane. his necessitates the downward tilting of the elevating rudders 12, which are shown as ivoted at the rear of said tail pieces 11. ut while the fore and aft balance of the aeroplane may be restored and maintained by operation of the controls by the aviator, this places a constant strain upon the aviatorsince the bearing of the'elevating rudders is forward of the center of pressure, and also as will be seen, a braking effect will be exerted on the aeroplane by the rudders in this position.

It is to overcome these objections that I have adopted the arrangement and operation of propellers herein described. x

The slip stream from a revolving propeller assumes the character of a helixof airv as shown by the arrows 13. I propose to use the upward trend of this helix to neutralize the'efect of the air currents 10 upon the horizontal tail planes 1l by pressing upwardly under said planes at 14, or by pressing upwardly on the air currents 10, so that the meeting of the upward currents 13 and the downward currents 10 will produce a current 15 flowing straight back so as not to press either upwardly or downwardly on planes 11. In reality, both of these results are produced, so that the stabilization is effected partially by the upward pressure of currents 13 on planes l1 and partiall by the straightening out ofcurrents 10. eans may also be provided for alining planes 11 with the currents 15 as shown by dotted lines 20, to secure the final adjustment. To this end, any suitable uides 19 on the ends 16 of planes 11 may e moved through a slotted member 18, and fastened in the desired position. This shifting of the inclinaif desired, be placed under the control of the aviator, by means of la lever 21 near the aviator, having wires 22 connected thereto and passing over pulleys 23 and fastened to guides 19. The tail planes *'11 are situated preferably midway A CORPORATION OF NEW.

between the axes of revolution of the propellers, and as shown in lFig. 4, may be in substantially the same horizontal plane therewith. In reality, however, the propellers may be a little above or belowvthis plane depending upon the depressing force of currents 10, which will vary under varying conditions, as for instance, with differently curved lifting planes.

In Fig. 6, I have shown the' tail surface 11 and elevating rudder 12 supported by struts 24, in a position above the rear end of the fuselage or body 3 of the aeroplane. B this arrangement, the said surface and ru der may be removed from the influence of the depressing currents 10, and at the same time be acted upon by the upward Whirl 13' of the propeller slip streams, to a suflicient extent to counteract the effects of the depressing currents 10 upon the rear end of the fuselage 3. The distance of plane 11 and rudder 12 above the fuselage will of course vary according to the type of propellers being used, or the length of the propeller blades, or the power of the engines, under which conditions the lifting effect of the slip streams at a given relative point will vary. Also, the said plane 11 and rudder 12, instead of being removed entirely from the path of the depressing currents 10, may be located in said path at a point where the resultant of the meeting of currents l0 and 13 have neither aA depressing nor a lifting effect upon said plane and rudder, or preferably, where the said resultant causes a slight lifting of said plane and rudder, sufcient to counteract the aforesaid downward pressure of currents 10 on the fuselage.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of my invention, together with the apparatus which I now con sider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combination and relations described, some of thesemay be altered and others omitted without interfering with the more general results outlined, and the invention extends to such use. y

Having described my invention, what I desire to secure by Letters Patent is:

1.- In an aeroplane, a vsustaining plane, a tail plane supported in the rear thereof and a pair of propellers positioned forward of said sustaining plane and on opposite sides of the` fore and aft center-line of the aeroplane, said propellers being adapted to rothe depressing currents produced by said sjistaining plane adjacent said tail plane.

2. In an aeroplane, a sustaining plane, a tail plane supported in the rear thereof,

a pair of propellers positioned forward of 4the slip streams produced thereby will impinge the depressing currents produced by said sustainlng plane adjacent said tail plane, and means for shifting the fore and aft inclination of said tail plane.

v3. In a tractor aeroplane, la supporting plane, a tail plane, means for neutralizing the downward pressure of air currents from said supporting plane on said tail plane, comprislng a pair of oppositely pitched propellers and means for rotating said propellers in opposite directions with their inner tips moving upwardly, whereby the upward whirl from said propellers will meet said depressing currents adjacent said tail planes.

4. In a tractor aeroplane, a supporting plane, a tail plane, means for neutralizing the downward pressure of air currents from said supporting plane on said tail plane, comprising a pair of oppositely pitched propellers and meansfor rotating said propellers in opposite directions with their inner tips moving upwardly, said propellers being so positioned that the upward whirl therefrom will meet said depressing currents ad-y jacent said tail planes.

5. In a tractor aeroplane, a supporting plane, a tail plane, a pair of oppositely pitched propellers, means for rotating said propellers in opposite directions with their inner tips moving upwardly, whereby the upward trend of the whirl from said propellers will impinge the lower surface of said tail plane, and means for shifting the angle of said tail plane, wherebyl the effect of the depressing currents from said supporting plane and the lifting e'ect of said upward trend of said whirl upon said tail plane may be equali'zed.

6. In an aeroplane, a supporting surface, a tail surface situated in the downwardly pressing currents from said supporting surface, and means for forcing a current of air upwardly against said tail surface for neutralizing the depressing eHect of said downwardly pressing currents.

7. In a tractor aeroplane, the combination of a plurality of supporting surfaces, a fuselage, a pair of propellers adapted to be driven in opposite directions with their inner tips moving upwardly, and a horizontal tail surface on said fuselage positioned in the current resulting from the meeting of the depressing currents from said supporting surfaces and the upward trend of the slip stream from said propellers, at a point where the lifting effect of said resulting current upon said tail surfaceis equal to the depressing effect of said depressing currents upon said fuselage.

8. In a tractor aeroplane, the combination of a supporting surface, a pair of propellers adapted to be driven in opposite directions with their inner tips moving upwardly, and a horizontal tail surface at'- tached to said aeroplane in the current resulting from the meeting of the depressn currents from said supporting surfaces an the upward trend of the slip stream from said propellers.

9. In an aeroplane, a main supporting surface', a pair of propellers 'adapted to be rotated with their inner tips moving upwardly, and a stationary and a movable tail plane positioned on said aeroplane in the stream produced by the meeting of the depressed air currents from said supporting surface and the upward trend of the slip stream from said propellers.

In testimony whereof I have affixed my signature.

LAWRENCE B. SPERRY. 

